Control transformer is an isolation transformer which is used generally in an electronic circuit that requires constant voltage with a low power or volt-amp rating. Control transformers are designed to provide a high degree of secondary voltage regulation for a short period overload condition, which is called or referred to as inrush. Control transformers are sometimes also called industrial control transformers, machine tool transformers, or control power transformers.

Control transformers supply all kinds of electrical circuits like measuring and controlling circuits, powering electronic circuits, controlling circuits, switch gear and distribution systems, machines to step up or step down transformers and others.